This invention relates to improvements in and relating to a burning furnace adapted for the combustion of wastes such as city- and/or industrial wastes.
Burnable wastes, dusts and/or garbages discharged from our daily life are subjected to gradual change in their kind and nature with rapid improvement of the living standard. More specifically, these wastes have lesser and lesser water contents and larger and larger synthetic resin contents as the civilization advances. In this respect, conventional wastes burning furnaces, especially of small capacities, have been designed to treat such wastes as of rather lesser heat calories, and it has been found that when such conventional furnaces are utilized to burn out high caloric wastes abundant of synthetic resin contents, too much amount of excess calories and corrosive and errosive gases are generated during the burning service so that the metallic gratings and the like furnace components may soon be injured. Therefore, conventional wastes burning furnace, it is substantially impossible to burn plastics wastes. Thus, it is desired among those skilled in the art to provide a burning furnace adapted for burning plastics wastes or those containing abundantly plastics.
When plastics-containing wastes are being burnt, the combustion air must be supplied more abundantly than otherwise. If the flow of the supplied air is not evenly distributed, the burning becomes incomplete and the exhaust gases include a large amount of soot. In addition, tarry substances will be produced and flow down to the grating which is thus clogged. Further, the exhaust gases include corrosive components such as HCl; SO.sub.2 ; SO.sub.3 and/or HCN which attack corrosively the grating, ash scraper and the metallic parts of and for the furnace.
For solving the above problems, we, as coinventors, have already proposed a large size burning furnace which is provided with a conveyor arranged at the bottom thereof and a layer of mineral particles is continuously provided so as to form a furnace bed which is adapted for burning the wastes casted thereon and taking out unburnt residuals from the downstream end of the moving conveyor (refer to Japanese Patent Application Sho-46-101, 925 matured into Japanese Patent No. 830,943). By the provision of the layer of mineral particles, acting as the furnace bed, any contact of the waste under burning and of the exhaust gases developed, with the metallic constituents of the furnace, can be effectively avoided and it is possible to supply a plenty of air through the pervious furnace bed and for the combustion purpose and to realize complete combustion of the wastes by avoiding otherwise possible clogging of the grating by sticky and tarry burning residual which may flow down from the waste mass towards the grating.
With such large size burning furnace as above described and having a movable furnace bed of large operating surface area adapted for treating large amount of the wastes to be burnt, it has been found that substantial difficulty in effective supply of the combustion air into the combustion chamber of the furnace, and indeed, through the moving furnace bed from below. In order to satisfactorily supply the combustion air in the required large amount, it is necessary to cover and enclose the lower part of the furnace, including the conveyor, so as to form a kind of pressure air chamber in and by the enclosure. Since the unburnt residual is taken out together with the mineral particles forming the furnace bed, and then, the both these must be continuously sieved out from each other, so as to reutilize the thus separated mineral particles again as the renewed furnace bed material, upon having been conveyed back to the initial conveyor by means of a separate conveyor. Thus, the whole arrangement of this type of burning furnace becomes too much large and complicated to be practically adopted.
On the other hand, smaller capacity burning furnaces than 10 tons per day, having substantially no metallic parts liable to contact with burning material and/or combustion gases and a stationary furnace bed, are highly desired by and among the consumers.
However, when it is desired to provide a wastes-burning furnace fitted with a stationary grating having a layer or mass of mineral particles, in order to dispense with such metallic furnace component(s) as liably contacting the combustible material and/or the combustion gases, substantial difficulty will be met in the provision of the pervious mineral furnace bed and in the discharge of the ash and the like unburnt residual, especially adapted for use with smaller capacity burning furnace for burning plastics-abundant combustion material.
It is therefore the main object of the present invention to provide an economical and smaller capacity burning furnace having a stationary type furnace bed and highly adapted for burning wastes containing substantially exclusively or abundantly plastics.